Seeking advice on most efficient moderate lumen optics, driver, led (FT03 or some C8/M21?)

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Sijaro
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Seeking advice on most efficient moderate lumen optics, driver, led (FT03 or some C8/M21?)

Dear lumen and candela obsessives, illumination technics scholars and flashlight lovers,

I fell down a rabbit hole reading intensively for weeks on this forum and other places about flashlights after some stressful nightriding in the hills with a too dim and brief shining mini-light.

Could you advise me in my quest? I cannot arrive at a dependable conclusion about which light is most suitable and efficient for nightly gravel rides in hilly forests and fields while on wild camping travles without regular recharge.
Given the rare recharges and limited amount of spare batteries, I would try to ride for as long as possible on minimum lumen:

- For MINIMA, I imagine around 200-400lm and 75-150 usable throw should be sufficient to anticipate differnet surfaces, gradients, obstacles at 22km/hr to 34km/hr. Is that fair?

- For LED, I am leaning towards the SST40 though it is not the most efficient. Is it nonetheless an efficient compromise in the tradeoff between its Lm/Watt, useful throw and spill? (alternatives: SST70, XPL-hi, XHP35/50/70).

- For DRIVER the FT03 only has regulated current till 150lm, is that correct? Would such FET+1 driver be significantly less efficient at 200-400 lm? Which of the others would then be the best choice in driver: C8G, C8+, M21A ?

- For FIRMWARE stepped ramping seems best (unless a “low” or “medium” matches a fitting strenght): fine tuning, and with consistency. Now, is there a difference in efficiency with C8+‘s 4mode/12group/Ramp.//C8G’s/FT03’s?

- For OPTICS, I am leaning towards the FT03 since with 1/3 more throw I may lower the needed lumens and save watts, correct? I read on BLF that the optics of Sofirn’s, Astrolux’s and Convoy’s C8 (+M21A) are identical, right?

- For Anti-GLARE, I could make a ‘reflector shield’ but perhaps there are TIR lenses that would do the trick much better? I could only find 17,20,33mm tir lensen. Can anyone find some for C8 models or for the FT03?

After comparing all reviews of beam patterns, throw and tail currents/runtimes I think of going with the FT03 SST40. Is that a good choice?

Many thanks for your invaluable help!

Edited by: Sijaro on 02/15/2021 - 16:30
Tater Tot
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The driver used and LED used will make a big difference in lm/W.

FT03 has a pretty bad efficiency due to driving a small LED hard and the driver is FET+1, which is rather inefficient.

The Convoys with boost driver and XHP50.2 and XHP70.2 is probably what you are looking for.

Convoy M3-C seems like a good fit, as it runs around 140 minutes on ~1500 lumens with a 5000mAh 26650 cell. And much longer at lower levels.

Review of Convoy M3-C here.

alpg88
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you want efficiency forget linears or fets, you will turn your battery power into heat first half of the useful range, go for xhp50\35 and a boost driver,

CNCman
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Tater Tot wrote:
The driver used and LED used will make a big difference in lm/W.

FT03 has a pretty bad efficiency due to driving a small LED hard and the driver is FET+1, which is rather inefficient.

The Convoys with boost driver and XHP50.2 and XHP70.2 is probably what you are looking for.

Convoy M3-C seems like a good fit, as it runs around 140 minutes on ~1500 lumens with a 5000mAh 26650 cell. And much longer at lower levels.

Review of Convoy M3-C here.


.
I like the Convoy M21C-U also for efficiency. Wink https://1lumen.com/review/convoy-m21c-u/#conclusion
.

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Sijaro
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Thanks for your feedback!

Based on my calculations from reviews and data sheeds, the SST40 has ca. 87% of the efficiency of the XHP50.2 at lower lumens. I thought this difference would be more than compensated by the higher increase in throw.
(more throw would allow me to use less lumens and thus less battery). The same reasoning I had that 50% increase in throw with FT03 might more than compensate the less hight increase in inneficiencies of the FET+1.
Note that the M21C/M3 seem rather flood torches with almost half the throw of the C8 with SST40. Am I misguided in these conclusions? Can these tradoffs be assessed is some way numerically?

Are constant current drivers of the C8+, M21A (C8F?) less efficient than boost drivers of the M21C/M3 (does the 3V XHP50.2 require boost?)? Are there differences in efficiency between the firmwares, e.g. 4mode/12group/Ramp of the drivers ?

Have a great weekend meanwhile!
Simon

EDIT: I should specify that I impulsively bought this week a floody headlamp(D25S 2xSST40). however, I think I would be better served with a thrower with narrower beam than XHP50.2 which seems to waste too many lumens on the sides, no? SST40 I believe could be run on less lumens with enough but less spill so as to preserve more night vision up close and reach in the distance to anticipate obstavles in surface or gradient or direction. Is my reasoning sound or not?

ArturoSC1
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Tater Tot wrote:
The driver used and LED used will make a big difference in lm/W.

FT03 has a pretty bad efficiency due to driving a small LED hard and the driver is FET+1, which is rather inefficient.

The Convoys with boost driver and XHP50.2 and XHP70.2 is probably what you are looking for.

Convoy M3-C seems like a good fit, as it runs around 140 minutes on ~1500 lumens with a 5000mAh 26650 cell. And much longer at lower levels.

Review of Convoy M3-C here.

3.500 lumen/hour from 5Ah? Really?

Sijaro
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To clarify: turbo and high or their runtimes as such are irrelevant to my purpose.

(This touches upon a sore spot for me in reviews that often check runtimes in turbo & high but not in the to many more relevant lower modes. Also the variety in the presentation of results and methods makes it difficult to arrive at a substantiated decision. Some tail amps reults I cannot trust or make any sense of [lack of testing protocols e.g. direct drive currents changing with the battery charge?], for example can it really be true: 700lm @0,39A in www.zeroair.org/2019/01/01/sofirn-c8f-21700-flashlight-review/#Modes_and... ? With other multi emitters I saw no rise in efficincy compared to single emitters in the tests. Someone here does?)

Anyway back on topic: what about the efficiency of the various constant current drivers and their various firmwares in the C8/M21A models compared to the perhaps not so ineffiecient tradeoff of 1/2 moree throw in FT03?

alpg88
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Sijaro wrote:

Are constant current drivers of the C8+, M21A (C8F?) less efficient than boost drivers of the M21C/M3 (does the 3V XHP50.2 require boost?)? Are there differences in efficiency between the firmwares, e.g. 4mode/12group/Ramp of the drivers ?

?

all drivers are constant current, that is their purpose to provide constant current. there are boost, buck, boost-buck, and linear drivers.
linear are least efficient, they are pretty much regulated resistors, that turn excesses power into heat, if your led is 3v led, but the cell has 4v in it, linear driver will turn that 1v into heat, wasting energy, when the battery drains to the voltage close to what leds needs, it becomes more efficient than before, you can measure current in and out of a linear driver, it will be the same, just like with a resistor.

other drivers are not wasting energy as much, they are also called switching regulators, zebralight uses boost-buck drivers, for 18650 lights, that are more efficient that other lights that use linear drivers, for your purposes, for sst40 the most efficient for low current would be buck-boost, but i do not know of any that are available in 17mm. that is why i suggested higher voltage led, and a boost driver, it would be more efficient for your purposes than a linear driver, or a fet, which is really a direct drive, and linear regulations at low currents, maybe there are fets that have boost-buck regulation at lower currents, but i do not know of them

Sijaro
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I thought not all drivers are constant current, i.e. that direct drive (fet) are not constant current, hence the decrease in current and lumens as the battery empties? (budgetlightforum.com/node/33820)
Also linear drivers (such as those in the C8+/M21A) though heating away excess on hight, still averaging an efficiency of 89% over the whole run, I had understood. (ib.)
It was not clear to me whether the usually included buck or boost drivers were more efficient than that? I have not noticed any difference to that effect in tests with tail currents or runtimes so far, except that the XHP50.2 3V and the XPH70.2 6v do have better runtimes (is the 50.2 led provided with a boost driver despite its 3v?). However, their halving of the throw and their spill of lumens to the side makes perhaps for more efficiency loss than the lm/watt gain from the boost driver and the led?

These are the kind of questions that have been unanswerd in my head the past few days: what are the resulting efficiencies in the tradeoffs between throw, beam pattern, led/driver efficency, stepped dimming or 12mode, etc.

ArturoSC1
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Buck/boost may be 95% efficiency when linear may be 70%

Sijaro
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It implies here for linear 78% on full charge but on average 89%. Is this wrong? www.budgetlightforum.com/node/33820

95% are these values for the buck/boost drivers used by the regular convoy, sofirn, … models?

merlot
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Not all drivers are constant current, such as a driver which uses PWM. I believe basically all FET + 1 drivers use PWM which, even if it is too fast to see, is still less efficient.

alpg88
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Sijaro wrote:
It implies here for linear 78% on full charge but on average 89%. Is this wrong? www.budgetlightforum.com/node/33820

95% are these values for the buck/boost drivers used by the regular convoy, sofirn, … models?

could be correct, until battery voltage meets led Vf linear drivers are terribly inefficient, if you looking for efficiany, you need the driver to be efficient at entire voltage range, battery cuts off at 2,7v, so linears are only very efficient between 3 and 2,7v range, from 4,2v to 3v they burn energy away, especially when we are talking low current, (200-400lm) , it will take a while for the cell to drain to 3v,

i do not think sofirns and convoys use boost-buck, when it comes to 3v led and 1 cell lights, they use linear drivers,

yes fets are not regulated, they are basically direct drives, no regulation at all, except for some in low modes, that have linear regulation, fet +1 or +2, means 1 or 2 amc linear regulators, others just use pwm for dimming.

i’m not sure what beam pattern has to do with electrical efficiency, it has no effect on it, optical efficiency, yes. you can find that number in optic datasheet, no guesses needed,

as far as firmware, not sure . it may affect electrical efficiency in some ways, or it may not, maybe someone who designs drivers will come and comment on that
ggf31416
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There is a tradeoff between large emitters with high efficiency and low throw (XHP70.2) and small emitters with lower lumens but higher throw (CULPM1). LEDs run happier a low power per area. The XHP35 HI would be in the middle, but the large 3.7V->12V often lowers the efficiency for boost drivers in turbo mode. If you need maximum throw maybe consider the M21C with CULPM1.TG 8A or the equivalent L21A, that 8A driver is a buck, bigger head means more throw. The mode spacing is not so good for the low modes, at the 10% level you would get about 240lm which may be ok for your needs. Mocarny got 132 minutes @ 680lm with a 3000mAh Samsung 30T , another review. Of course efficiency won’t be as good as the XHP70.2 but maybe the throw can compensate.

Edit: C8F 700lm @ 0.39a = 700lm / 1.7W = 400 lm/W is nonsense. Note that the 700lm is claimed by manufacturer, not measured by 1lumen.

alpg88
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yep, larger dies or multiple die leds are generally more efficient when it comes to lm\watts.

for 200-400lm light, spec’d out for max efficiency you can not get more efficient than 50.2+boost, with parts readily available.

kramer5150
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As far as optical efficiency goes, large/deep throw reflectors are generally less efficient than small shallow flood types. So for best optical efficiency, use as small + shallow a reflector as possible. The more side emitted light you reflect forward, the less optically efficient the design will be. Even the best quality reflectors are not 100% reflective. The most efficient optic is none, just the bare LED on a heatsink body. Those are typically referred to on BLF as mule lights. I never cared for those though because they blind everyone within the vicinity, including the user.

[EDIT] disregard this (mule) completely as a realistic solution for your application as a bike light. Somehow I missed that part of the discussion.

ggf31416
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In term of lumens yes, but effectiveness (to avoid saying efficiency) in real world also includes how much light reaches the objects you want to see.

Sijaro
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Right! Though big dies are more efficient in lm/watt they are not necessarily most efficient in “usefull.beam/lm/watt”. Indeed, effictiveness may be a better word here. Smile I have not enough nightbiking experience but I would guess: say, a gravel road of ca. 4 meter width at a distance of ca. 100 meter. I think a throw par excellence osram led would be too narrow, though. Or not? A bit of low light spill in frónt of the bike and perhaps some on the side (without harming night vision) would be desirable.

pennzy
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This tube light impresses me with it’s Osram P9 emitter and buck driver. The beam is throwy yet wide enough to be useful. 2.5 hours of 400 lumens.
https://www.wubenlight.com/products/wuben-l50-1200-lumens-led-flashlight

kramer5150
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For my gravel trail / XC rides, and work commutes I have been using a fenix E35UE for a few years. It’s an older light, less efficient by todays standards but it has proven to be reliable and will maintain about 350~400 OTF constant ON. Nice floody multi-purpose beam, that throws far enough for my needs. Since my top speeds are only around ~10-15 mph. I dont need to see way out. I just need to be careful of squirrel, rabbits and wildlife that can dart out onto the trails.

I always carry a couple spare 18650 cells in my pack, and a SF6P as backup. The last thing I want is to be stuck somewhere with no way to light up the trail

Sijaro
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Thanks for the imput. Yes, I would need to see some distance to anticipate problems at my speed. That Wuben seems to have very short runtimes in comparion with e.g. the Lumintop B01 which has nearly 5 hous at over 450 lumens if run on a 4Ah battery, but has modest throw of 200m (how much of this is useful though?).

kramer5150
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You need to figure out your stopping distance at top speed to estimate illumination throw distance. Stopping distance varies significantly from rider to rider over various declines and terrain types. Your illumination reach needs to out throw this distance, so you can spot hazards with enough distance to come to a stop before hitting them. You never want your stop distance to exceed the range of your visibility (in general… day and night).

The safest answer to this, without knowing your actual stop distance is “the more lux and lumens the better”. Better to have and not need than to need and not have. Of course theres a trade-off penalty to this philosophy, cost, size, weight…etc.

I am not familiar with that Lumintop B01. Looks like a nice setup for starters. It has a unique looking reflector, designed not to blind oncoming traffic. Not sure how useful this would be on the trails though. In the spirit of your original post requesting efficiency, I am not sure how it blocks light from oncoming traffic. Does it simply obstruct (entrap) that light? or does it reflect/re-direct it OTF? The former would be less desired for lumens/watt efficiency. I personally prefer a traditional reflector, and I just aim it down to the ground a little.

Rattlesnakes are also a common trail hazard in my area. They come out at night to hunt nocturnal rodents and sun themselves on the trails during the day.

pennzy
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Sijaro wrote:
Thanks for the imput. Yes, I would need to see some distance to anticipate problems at my speed. That Wuben seems to have very short runtimes in comparion with e.g. the Lumintop B01 which has nearly 5 hous at over 450 lumens if run on a 4Ah battery, but has modest throw of 200m (how much of this is useful though?).

The Wuben comes with a rather low capacity 18650 (2600). The Lumintop is probably using a 5000 mah 21700 for run time estimates.
pennzy
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Sijaro wrote:
Thanks for the imput. Yes, I would need to see some distance to anticipate problems at my speed. That Wuben seems to have very short runtimes in comparion with e.g. the Lumintop B01 which has nearly 5 hous at over 450 lumens if run on a 4Ah battery, but has modest throw of 200m (how much of this is useful though?).

The Wuben comes with a rather low capacity 18650 (2600). The Lumintop is probably using a 5000 mah 21700 for run time estimates.
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Dont forget bike mounting too (!!).
The handlebar mount I show in my pic is only good for smooth trails, slow speeds and urban commuting. So its OK for me but I would not recommend it openly.
A better / safer recommendation is something like this one here:
https://www.amazon.com/gp/product/B088WH6HBM?pf_rd_r=JT3ZP84D6DECH5D91Q9...

A heavier / bigger light like a 21700 with onboard USB charging will require a more robust mount (all else being equal). For me personally I prefer a small / compact light on my bars, and I just bring extra 18650 battery or two in my pack along with my trail tools, spare tire tube, patch kit…etc. Since I’m generally not in a hurry when I am on my bike, its no biggie to stop and swap cells. But this feeds back into my overall preference to keep the bike as light & nimble as possible. Any added weight from my tools, lighting and hydration is in my pack… not mounted to the bike.

I didn’t see it mentioned yet but you should also confirm PWM. On an active use trail/road light you don’t want any PWM at any mode. I would consider this a deal breaker for a bike light.

Sijaro
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pennzy wrote:
The Wuben comes with a rather low capacity 18650 (2600). The Lumintop is probably using a 5000 mah 21700 for run time estimates.
No with 4Ah as I had calculated in the post above. The tests of were done with 2.6Ah battery running 2hours30 at 467 lumens so that is not very dissimilar indeed. Smile

- Right about stopping distance. It would also vary with the incline and the state of my breaks. A speed of 28km/h recalculates seven meters per seconde so that an effective throw of 100 meter should give me a decent 15 seconds of anticipation time.
- That mount you link to was the one I had decided on. They go for cheap on aliexpress.
- PWM, I would like to avoid too. Mostly an issue on direct drivers, no (e.g. FET +1 should have no PWM for the lumens that use the linear driver but those lower lumens that go beyond that driver would have PWM?)

Sijaro
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kramer5150 wrote:
…I am not sure how it blocks light from oncoming traffic. Does it simply obstruct (entrap) that light? or does it reflect/re-direct it OTF?
I though I would just have to live with the nuisance of lights from oncoming trafic and can’t imagine how a reflector could catch it (though I could imagine a light on high or turbo being on the same level and hence reducing the hindrance though depleting the battery). Could you explain this a little further?
ArturoSC1
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Lumintop B01 has a horizontal projection and the lumens cannot be compared to those of round spot lamps

Agro
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If you want a LED that is efficient while offering some throw, something domeless with large die will be better than a domed LED.
See this 2-years old compilation to learn more:
https://budgetlightforum.com/comment/1339991#comment-1339991

BTW, I thought that it would be nice to update this chart with newer data….and I can’t.
Koef3 is not here nowadays.
djozz has mostly ceased testing.
Texas Ace has ceased testing.
maukka? No LED review from him in almost a year (though I think he’s done some quick tests since then).

There are some new people filling the gap but not many of them and doing mostly quick tests rather than full fledged reviews.

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While more light and throw is always better, back when me and my buddies were hitting singletrack at night, it was amazing how effectively you could see with diminishing output as the eyes adjusted. For example, a 100 lumen helmet mounted light was quite adequate in the dark. Now, if you are competing against street lights, shadows, cars, etc it will feel different. But in the dark on the singletrack it was surprising. Now, I usually rode with more than that (a triple SSC P4 on the handlebars as well) which was amazing.

Don’t focus solely on throw, either. A pencil beam is going to give you an uncomfortable, tunnel vision experience. I really liked the triple SSC P4 because it offered wonderful spill. Worked amazing with a semi-throwy helmet light. Whatever you do, don’t stick a lone thrower on your bars and expect a good experience. Something like my Convoy S2+ SST-20 with OP reflector gives and excellent helmet light beam. If you did the 7135×3 driver, 35% mode gives and estimated 126lm for 8+hrs.

Here is a chart I built with the help of BLF member tests. The lumens are generally estimated and the runtimes are calculated. And altough I forget what mAh I used for the calc, simple math can tell you that Wink

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I would use a head lamp and a single cell light handlebar mounted, that’s what I do on my Xc bike. I do a KR4 on the handlebar mount with the Olight handlebar mount (nice piece for about $12) and a sofirn sp40 headlamp. Both can maintain around 400 lumens (guestimate) for a while (over a couple hours) if you don’t put them on turbo/blast mode for more then a couple seconds here and there.

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